Transplantation and inflammation : role of chemokines, microRNAs and extracellular vesicles

Abstract

Ischemia reperfusion injury (IRI) is an inevitable occurrence during the process of organ transplantation. The biphasic nature of IRI subjects the allografts to two distinct inflammatory insults which can affect the short-term and long-term outcomes of the allografts post transplantation. This thesis aimed to address the implications of several dysfunctional cellular processes as a result of ischemia. Firstly, I show that the excessive presence of reactive nitrogen species can result in protein post translational nitration. In particular, I focused on CXCL8 and showed that nitration impaired its capability to orchestrate neutrophil migration during reperfusion injury. Furthermore, this modified CXCL8 was identified in bronchoalveolar lavage samples from patients with ventilator associated pneumonia using a novel antibody and validated with mass spectrometry. Secondly, transcriptional profiling of renal glomerular endothelium showed upregulation of miR-210 when subjected to hypoxia. This was accompanied by a perturbation in cellular metabolism. Our work showed that overexpression of miR-210 upregulates renal glomerular endothelium glycolysis but mitochondrial function remained unaltered. Finally, I examined surface marker expression on extracellular vesicles (EVs) derived from renal allografts microvasculature. EVs derived from deceased allograft donors showed higher expression of class II major histocompatibility molecules (MHC class II) as well as signatures associated with endothelial activation. This high expression of MHC class II was also recapitulated in vitro, suggesting that endothelial derived EVs might play an essential role in potentiating allorecognition. This mechanism could be responsible for maintaining long-term response of alloreactive T cells against allografts. Collectively, I have shown several cellular processes that are regulated in response to ischemic damage to either function as a priming or a resolution mechanism within the allograft to elicit a secondary inflammatory response during the reperfusion phase of organ transplantation.